1. Field of the Invention
The present invention relates to a barrier apparatus of a camera for opening and closing a photographing opening of a lens barrel.
2. Description of the Related Art
A recent camera has a barrier apparatus (barrier unit) incorporated therein for opening and closing a photographing opening. The barrier unit is mounted to the front end of a lens barrel which is movable in an optical axis direction between a photographing position in which the barrier is opened and a retracted position in which the barrier is closed. In the retracted position, the lens barrel is retracted to a rearmost position within a camera body. In the photographing position in which a picture can be taken, the lens barrel is advanced forwardly from the retracted position to open the lens opening.
There are two types of barrier units, i.e., a normally open type and a normally closed type. In the normally open type of barrier unit, the photographing opening is normally opened by a spring when the barrier unit is not attached to the lens barrel. When the barrier unit is attached to the lens barrel, the barrier is closed if a load is applied to the barrier in the retracted position and is opened if no load is applied to the barrier in the photographing position.
In the normally closed type of barrier unit the photographing opening is normally closed by a spring when the barrier unit is not attached to the lens barrel. When the barrier unit is attached to the lens barrel, the barrier is opened if a load is applied to the barrier in the photographing position and is closed if no load is applied to the barrier in the retracted position.
It is quite easy to attach the normally closed type of barrier unit to the lens barrel if the lens barrel is positioned at the retracted position upon assembly. However, in practice there is a necessity to attach the normally closed type of barrier unit to the lens barrel at the photographing position of the lens barrel. For example, if the attachment of the normally closed type of barrier unit is performed at the retracted position, there is a possibility that the light intercepting block, which closes a gap between the inner peripheral surface of the immovable lens barrel which surrounds the lens barrel and the outer peripheral surface of the lens barrel may be clipped, thus resulting in a decreased light intercepting effect. Accordingly, the attachment is a time consuming operation. In view of this, the normally closed type of barrier unit should be mounted to the lens barrel in the photographing position rather than the retracted position.